1. Field of the Invention
The present invention generally relates to socket wrench sets, and more particularly, to socket drivers with tool bit retaining protuberances for retaining the driven members in the drive sockets.
2. Description of Prior Art
Typically, it is important to retain driving and driven members in coupling engagement with each other during use. While it is also important to be able to selectively separate these members from each other, such as for interchanging or replacing driven members to suit a particular application, it is frequently desirable to semi-permanently attach the driven members, such as bit drivers, to the driving members, such as socket drivers. In those instances, while it is desirable to remove the driven members under certain circumstances, the intention is to maintain the driving and driven members in coupling engagement with each other during normal use. One common approach for coupling a drive bit to a drive socket, for example, is the use of a coupling pin which extends diametrically through transverse holes through the engaged members. However, this approach has the disadvantage that it requires separate additional parts. Also, the bit and drive socket must have the transverse holes therein perfectly aligned with each other and accurately sized to securely receive the pin. Otherwise, the pin may become loose and fall out or may be sheared in use. This approach is relatively costly to manufacture.
Another common retention technique utilizes a spring-biased ball in the bit which is engagable with a complimentary recess or groove in the socket. This, again, involves a costly construction requiring the assembly of multiple parts.
In addition to the added manufacturing costs with the aforementioned techniques, engagement and disengagement of the bits and the sockets is relatively cumbersome and time consuming, requiring the mounting and demounting of a set screw or roll pin, each time the bit is changed. In fact, it is frequently so cumbersome to change set screws or roll pins that normally a user will purchase a separate socket for each bit to obviate the need for bit changing. The use of a friction ring for bit detention simplifies the changing but does not provide a very secure retention.
Clearly, the general use of one or more elements on at least one of the mating flat surfaces of a socket driver and tool bit for preventing inadvertent separation between the two during use is well known in the art. The use of a ball and spring arrangement has been commonly used for this purpose. Examples of patents which show this approach include U.S. Pat. Nos. 994,804 to Wahlstrom; 2,718,806 to Clark; and 5,309,798 to Markwart et al. In a number of cases, a spring element is used to urge a member, such as a stud, against a groove in the shank of a screwdriver bit, as illustrated in U.S. Pat. No. 2,010,616 to Walsh. In U.S. Pat. No. 2,523,041 to McKenzie, a screwdriver bit is provided with a protuberance on the shank of the screwdriver bit for engagement with interfering elements within the recess of the receiving cavity.
The problem which those in the art have sought to overcome is succinctly stated in column 1, lines 21-29 of U.S. Pat. No. 2,851,295 to Chaffee, where a ball and socket arrangement is disclosed.
A number of patents disclose the use of "O" rings intended to engage with recesses or regions of a tool bit. This is illustrated in U.S. Pat. Nos. 3,253,626 to Stillwagon et al., and 3,935,762 to Tudisco (see also U.S. Pat. No. 4,096,896 to Engel). The use of "O" rings and appropriate recesses in a bit driver are also illustrated in U.S. Pat. Nos. 4,328,720 to Shiel and 4,535,658 to Molinari.
In U.S. Pat. No. 5,295,423, a bit with frictional retention in the drive socket is illustrated in which appropriate recesses are provided in the flat surfaces of the bit itself. These are typically provided on opposing surfaces of the hexagonal bit configuration. The recesses cause the metal to flow outwardly and produce projections which extend above or beyond the flat surfaces of the bit. These projections fictionally engage the flat surfaces of the tool socket drivers. In U.S. Pat. No. 5,485,769 to Olson et al., FIG. 7 illustrates an outwardly projecting ear from the end surface of the bit.